Foster finds his niche as corn specialist, continues to examine potassium, phosphorus

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Matt Foster is finishing his second corn crop as the LSU AgCenter corn specialist, and he will tell you with each day, he is becoming more comfortable in the role.

One of his duties is to continue to perform on-farm demonstration trials across Louisiana. These research projects allow Foster and the farmers a first-hand look at how various corn hybrids perform in a real-world setting.

“This year we have 17 on-farm demonstrations in 15 parishes across the state,” Foster said. “We are looking at eight different hybrids at each location.”

He also is conducting research on the role of potassium and phosphorus as it pertains to corn yields.

“In 2021, two fields were used for the studies,” he said. “One was in Tensas Parish, and the other was in West Carroll Parish. Both fields were low in phosphorus and sufficient in potassium.”

Foster said the Tensas field was a silt-loam soil type with a phosphorus content of 13.1 parts per million. The West Carroll location was a clay-soil type and had a phosphorus level of 19.6 ppm level.

After applying additional amounts of both phosphorus and potassium at both locations, only the Tensas location saw a significant yield response.

“Our control group had a yield of 185 bushels per acre,” Foster said. “Adding 80 pounds per acre of each nutrient, the yield at the Tensas location went to 245 bushels per acre. Adding 120 pounds per acre of each nutrient got the yield to 269 bushels.”

Foster noted that applications for each group were done around the V3 growth stage.

According to Foster, these minerals are available for uptake immediately after a rain event. He also indicated that soil tests can be a very useful tool and can oftentimes indicate whether you can expect a response by adding fertilizer.

“It could be that actual ppm levels are more important than if a field is determined to be low or adequate with these nutrients,” Foster said.

This year, Foster is continuing this project in Tensas and West Carroll parishes.

Another project that Foster is involved with is examining the importance of crop residue.

Foster said that corn stover has value as a nutrient source. Generally, for every bushel of grain yield, the corn stover contains 0.45 pounds of nitrogen, 0.10 pounds of phosphorus, 0.60 pounds of potassium and 0.06 pounds of sulfur. Therefore, the stover of a 200-bushel per acre corn crop would contain 90 pounds of nitrogen, 20 pounds of potassium and 12 pounds of sulfur per acre.

When crop residue is burned, approximately 100% of nitrogen and 80% of sulfur will be lost upon combustion. In theory, phosphorus and potassium are not lost during combustion, but substantial loss can occur from the smoke and ash.

The loss usually occurs when ash floats away during the burn event or is moved away from the field by wind or rain after the burn. If the remaining ash is not immediately incorporated into the soil, up to 80% of the phosphorus and potassium could be lost.

Excessive removal of crop residues can eventually result in soil nutrient and organic matter depletion and require more fertilizer inputs. While the lost nutrients can be replaced, the loss of soil organic matter is not easy to improve. Foster encourages producers to let corn residue naturally decompose during the winter months instead of burning it.

The results of these projects may find their way into recommendations made by the AgCenter regarding corn production. Foster said this information is being shared with AgCenter soil fertility specialist Rasel Parvej and will be included with some of the findings of Parvej’s research. Craig Gautreaux

8/17/2022 8:22:29 PM
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